Svbony 8-3 zoom

[Mr Spock]

It's really good for doubles. Perfect airy disks in the Tak at x247 and 3mm. It takes me from x93 up to x247 and means I don't need as many eyepieces. Just a finder (42mm), closer finder (17mm), then this. Shame it's not par focal with anything. It has a lot more in focus than any of my eyepieces.

[IB20]

Currently £20 off on the large South American river website.

[Highburymark]

On 30/03/2024 at 18:27, Littleguy80 said:

It’s interesting to see how this impacts the secondhand market for short focal length eyepieces. I think the secondhand market is generally down a bit at the moment but seeing Delos, Pentax XWs and Tak TOEs sitting unsold in the classifieds makes me wonder if premium fixed focal length eyepieces are losing out to this extremely well priced quality zoom. I don’t really have a gap for it in my collection and I’m not sure how successful I’d be trying to sell other eyepieces to make space for it. 

At eighty quid and a long-awaited week in the Canaries around the corner, I have caved in and have a 3-8 on the way. Means I can just take three eyepieces away with me. It certainly covers an incredibly useful range for travel. Look forward to seeing how it compares to my other eyepieces in this range - a Delite, 3xTOEs, an XW, an XO, a couple of orthos and an Ethos. I’ll report back, particularly if it comes close to keeping pace with them!

[Mr_Cat]

36 minutes ago, IB20 said:

Currently £20 off on the large South American river website.

Thanks for the heads up - ordered

[Littleguy80]

34 minutes ago, Highburymark said:

At eighty quid and a long-awaited week in the Canaries around the corner, I have caved in and have a 3-8 on the way. Means I can just take three eyepieces away with me. It certainly covers an incredibly useful range for travel. Look forward to seeing how it compares to my other eyepieces in this range - a Delite, 3xTOEs, an XW, an XO, a couple of orthos and an Ethos. I’ll report back, particularly if it comes close to keeping pace with them!

That’s some tough competition, particularly the XO. Very much looking forward to your report. Have a great week in the canaries  

[Naughty Neal]

My second SV215 arrived today for BV use, again paid under £80 all in for it direct off of the SvBony website.

Also a gift T - shirt supplied in xxxl size, with a screen printed front of the planets and Svb insignia and the rear has the twelve zodiac constellations on the rear .

Also ordered via ebay some  ID 31.63mm  x 2 mm O - Rings to use as par focal rings incase the 1.25" is too long for my prisms/mirrors.

[Highburymark]

I’ve only had a couple of night sessions with the zoom so far, both with average seeing (on Moon and double stars), so still too early to form detailed impressions. Ergonomically no problems at all - mine is pretty easy to operate, not too stiff at all. The zoom action doesn’t feel quite as smooth and robust as the Nagler 3-6, but that’s a minor quibble. The optics are - as others have suggested - right up there with far more expensive eyepieces. I feel it’s at the two extremes of the range where other (I used Delite 3mm, XW 5mm and Baader zoom at 8mm for comparisons) eyepieces are marginally crisper. But I need to do more testing before making any definitive impression, particularly on planets. It’s bright and has good contrast. The biggest issue for me is lack of eye relief at 3-4mm. I can’t comfortably see the field stop at high magnifications without eyelash/lens contact. This might seem irrelevant when I have a Pentax XO 5.1 in my arsenal, which has even less ER (a ‘sporty’ 3mm, compared with around 6-7mm for the SV Bony), but with that eyepiece, I know I have to hang back, and therefore use it for short, critical detail views only. I couldn’t use the SV 3-8 at 3mm for long observations. But otherwise it’s clearly a really excellent little eyepiece. I don’t think it will beat existing class leaders, but for 95% of astronomers who don’t have problems with eye relief, it’s a single solution for planets, the Moon and double stars. Mine even came with a free T-shirt. 

[RT65CB-SWL]

On 16/04/2024 at 11:14, Highburymark said:

I’ve only had a couple of night sessions with the zoom so far, both with average seeing (on Moon and double stars), so still too early to form detailed impressions. Ergonomically no problems at all - mine is pretty easy to operate, not too stiff at all. The zoom action doesn’t feel quite as smooth and robust as the Nagler 3-6, but that’s a minor quibble. The optics are - as others have suggested - right up there with far more expensive eyepieces. I feel it’s at the two extremes of the range where other (I used Delite 3mm, XW 5mm and Baader zoom at 8mm for comparisons) eyepieces are marginally crisper. But I need to do more testing before making any definitive impression, particularly on planets. It’s bright and has good contrast. The biggest issue for me is lack of eye relief at 3-4mm. I can’t comfortably see the field stop at high magnifications without eyelash/lens contact. This might seem irrelevant when I have a Pentax XO 5.1 in my arsenal, which has even less ER (a ‘sporty’ 3mm, compared with around 6-7mm for the SV Bony), but with that eyepiece, I know I have to hang back, and therefore use it for short, critical detail views only. I couldn’t use the SV 3-8 at 3mm for long observations. But otherwise it’s clearly a really excellent little eyepiece. I don’t think it will beat existing class leaders, but for 95% of astronomers who don’t have problems with eye relief, it’s a single solution for planets, the Moon and double stars. Mine even came with a free T-shirt. 

If you have about a six inch square missing from the body of your T-shirt, then that will be my free lens cloth! 😉

Edited April 21 by RT65CB-SWL

[Mr Spock]

I'm going to use it for doubles and possibly planets. It has far too much field curvature for use in the 12" on the moon as I found last night. The effect is very similar to my 16mm Nirvana.

I tried it against my 8mm LVW, 7mm and 6mm orthos, and 6mm SLV.  They are all fine. I didn't get out the 7mm Nirvana this time but I know that is sharp to the edge on the moon. The Svbony was sharp in the centre, no more so than the others, with the 6mm ortho giving the best view, but that field curvature was annoying.

For lunar, if I want a wide view I'll put the Nirvana in, for fine detail, the ortho, and for high power, seeing permitting, the TOEs.

[Ags]

I haven't noticed FC much with the Svbony 3-8 despite using it quite extensively. I see the appalling FC of the Nirvana 16 clearly, so we agree on that! Next time I have a clear but Moonish night I will try it out again, paying more attention to the edges. Did you see this at all focal lengths?

[Mr Spock]

4 minutes ago, Ags said:

Did you see this at all focal lengths?

I only used 8, 7 and 6 due to the seeing. x253 at 6mm was enough 

[Louis D]

I don't recall FC being much of an issue, but the notes in my review/report does state I noted a tiny bit.  It must be pretty minor compared to my Pentax XL 14mm which I had to retire after my eyes went fixed focus in my mid-40s.  I'll have to look for FC in the Svbony the next time I have it out.

[Space Oddities]

First light yesterday evening for my Svbony zoom, which I received a few days ago. I only looked at the Moon early in the evening. 

I agree with everything people say about this eyepiece: it's really good! The views were amazing with my Tak FC-76DCU. Sadly Jupiter was very low on the horizon and not visible from my rooftop. I did try through the toilets window, but that wasn't easy  

I also agree with the minor annoyances, eye relieve at 3mm and the stiffness of the ring. But for 99€, that eyepiece is a bargain and definitely a keeper. I can't wait to try it out on planets once they're back into view!

Here is a pic I grabbed (with a Nagler, so that's just for context!)

[Mr Spock]

I haven't started my review yet. I still have to give it a full workout on the 4" Tak. On the 12" I was able to use it at the 5mm, 4mm and 3mm settings on the moon a couple of nights ago. Field curvature wasn't as evident as longer focal lengths and not intrusive. The eyepiece was sharp at all settings against the 4mm Nirvana, 7mm, 6mm and 4mm Circle-T orthos, 6mm SLV, 3.5mm and 5mm LVWs, with some variation - it wasn't a match for the 8mm LVW and the orthos looked 'cleaner'. It couldn't match the 4mm and 3.3mm TOEs in any area; the TOEs were sharper, clearer and had better contrast; they were able to pick up the tiniest of craters - I won't be selling them!

I did note the magnification looked the same as the 3.3mm TOE at the 3mm setting - objective rather than scientific. I also had to fold down the eyecup to feel comfortable. My tiny 4mm ortho was easier to look though!

[Highburymark]

14 minutes ago, Mr Spock said:

I haven't started my review yet. I still have to give it a full workout on the 4" Tak. On the 12" I was able to use it at the 5mm, 4mm and 3mm settings on the moon a couple of nights ago. Field curvature wasn't as evident as longer focal lengths and not intrusive. The eyepiece was sharp at all settings against the 4mm Nirvana, 7mm, 6mm and 4mm Circle-T orthos, 6mm SLV, 3.5mm and 5mm LVWs, with some variation - it wasn't a match for the 8mm LVW and the orthos looked 'cleaner'. It couldn't match the 4mm and 3.3mm TOEs in any area; the TOEs were sharper, clearer and had better contrast; they were able to pick up the tiniest of craters - I won't be selling them!

I did note the magnification looked the same as the 3.3mm TOE at the 3mm setting - objective rather than scientific. I also had to fold down the eyecup to feel comfortable. My tiny 4mm ortho was easier to look though!

Yep - the lower setting of the 3-8 is closer to 3.5mm I reckon.
 

[Don Pensack]

https://astro-talks.ru/forum/viewtopic.php?f=32&t=1483#p101290

Yup.  3.5-8.1mm

Review:

https://astro-talks.ru/forum/viewtopic.php?f=32&t=4585&p=94406#p94406

Edited April 19 by Don Pensack

[Highburymark]

I’m not picking up much field curvature at all - maybe it complements the opposite field curvature in my scopes? The 3-8 works well in all three of my refractors in this respect. In the F/6 60ED for example, just a tiny shift of the focus is needed at 3.5mm to make edge stars sharp. 
On the issue of parfocality, it’s very close to parfocal through the range. I don’t need to refocus between 8mm and 5mm, but below that, a small tweak required.

[John]

44 minutes ago, Highburymark said:

I’m not picking up much field curvature at all - maybe it complements the opposite field curvature in my scopes? The 3-8 works well in all three of my refractors in this respect. In the F/6 60ED for example, just a tiny shift of the focus is needed at 3.5mm to make edge stars sharp. 
On the issue of parfocality, it’s very close to parfocal through the range. I don’t need to refocus between 8mm and 5mm, but below that, a small tweak required.

Thats my experience with refractors as well. 

I don't have an F/5 newt to try it out in now.

 

[Mr Spock]

I notice in the Tak the field curvature seen in the f5 Newt isn't there. I'm guessing therefore it's f related. From 8 all the way down to 3 it's turning in a great performance. The difference between it and high end eyepieces is very small indeed and you could be happy (as a refractor owner) with this as your main eyepiece. I think f5 Newt owners should look elsewhere.

For the money it has to be the best bargain ever.

[Ricochet]

11 hours ago, Mr Spock said:

I notice in the Tak the field curvature seen in the f5 Newt isn't there. I'm guessing therefore it's f related.

It is the different types of telescope having field curvature that is in opposite directions. The zoom will be subtracting from the curvature inherent in the Tak and adding to the curvature inherent in the Newt. In fact, if it is your 12" you are talking about then the field will be effectively flat so the curvature you see is the true curvature of the eyepiece.

[jjohnson3803]

When I take my ST80 camping, I usually take 4 or 5 EPs along.  Maybe I should try one of these SVBs just to simplify my packing list.  🤔

 

[Don Pensack]

20 hours ago, Highburymark said:

I’m not picking up much field curvature at all - maybe it complements the opposite field curvature in my scopes? The 3-8 works well in all three of my refractors in this respect. In the F/6 60ED for example, just a tiny shift of the focus is needed at 3.5mm to make edge stars sharp. 
On the issue of parfocality, it’s very close to parfocal through the range. I don’t need to refocus between 8mm and 5mm, but below that, a small tweak required.

It is when curvatures match that you see a flat field.  When curvatures are opposite, the edge is far out of focus when the center is focused.

FC is always more of a problem with larger field stops, too, so FC will be less visible at the 3.5mm end than at the 8.1mm end.

[Highburymark]

9 hours ago, Don Pensack said:

It is when curvatures match that you see a flat field.  When curvatures are opposite, the edge is far out of focus when the center is focused.

FC is always more of a problem with larger field stops, too, so FC will be less visible at the 3.5mm end than at the 8.1mm end.

Yes indeed Don - but this has always made me wonder why we don’t see more people having field curvature issues with the many brands of flat field eyepieces (APM, Altair, Lunt, SVBony etc)? As there’s field curvature inherent in many telescopes. I haven’t used any of that range myself, and I don’t doubt they are excellent, but why buy flat field eyepieces unless your scope has a perfectly flat field?

[Louis D]

I buy flat field eyepieces to work toward with non-flat field scopes.  Once I added a coma corrector to my Newts, it reduced their low curvature even more.  I then added TSFLAT2 flatteners to my 2" diagonals to flatten my refractor fields.

I was even able to compensate for the field curvature of my 14mm Pentax XL by over-correcting the field flattening with the TSFLAT2 by increasing the working distance another inch or so, IIRC.  It was amazing to see the XL sharp edge to edge without refocusing.

[Don Pensack]

4 hours ago, Highburymark said:

Yes indeed Don - but this has always made me wonder why we don’t see more people having field curvature issues with the many brands of flat field eyepieces (APM, Altair, Lunt, SVBony etc)? As there’s field curvature inherent in many telescopes. I haven’t used any of that range myself, and I don’t doubt they are excellent, but why buy flat field eyepieces unless your scope has a perfectly flat field?

One reason I can think of is to reduce the amount of visible field curvature.

| + ) = )  You might be able to focus half way to the edge and accommodate the entire field.

| + | = |  This is ideal, and reflectors of 1200+mm focal length are pretty flat, so this will work.

) + ) = |  And this works if the eyepiece and scope have nearly identical curvatures,

) + ( = bad field curvature, and this can happen with a mismatch of eyepiece FC and scope FC.

Since we don't know (the manufacturers don't tell us) whether the FC in an eyepiece is positive or negative, the lowest risk is a flat field eyepiece.

But, alas, to the owner of a flat field scope, it doesn't matter whether the FC in the eyepiece is positive or negative--it'll be curved.

But, like the person with a flat eyepiece and curved focal plane scope, it might be possible to accommodate the curve, so the degree of FC is important as well.

I don't really under stand how short f/ratio refractors of 50-80mm don't see serious FC with nearly all eyepieces, though.

My 12.5" has a radius of curvature of ~1600mm.  An 80mm f/6 refractor has a ROC of 160mm!!  How any eyepiece wider than an ortho functions in such a scope is a mystery.

 

Edited April 21 by Don Pensack